Search found 4827 matches

by Jirka
Wed Nov 06, 2019 5:06 pm
Forum: Hydrus 1D
Topic: Competitive sorption, solute concentration initial conditions
Replies: 5
Views: 284

Re: Competitive sorption, solute concentration initial conditions

I think that for nonlinear and nonequilibrium solutes you can have only up to 5 solutes. Max 10 solutes are only for equilibrium conditions. J.
by Jirka
Wed Nov 06, 2019 2:41 pm
Forum: Hydrus 1D
Topic: terminating not converging Hydrus runs
Replies: 6
Views: 4748

Re: terminating not converging Hydrus runs

The code should automatically stop when it does not converge in 10 consecutive time steps. I'm not an expert on MatLab, but I believe you have there a command that would kill the run if it does not finish before some specified time. J.
by Jirka
Tue Nov 05, 2019 11:13 pm
Forum: Hydrus 1D
Topic: Competitive sorption, solute concentration initial conditions
Replies: 5
Views: 284

Re: Competitive sorption, solute concentration initial conditions

You can post those files right here in the forum (as others did). J.
by Jirka
Tue Nov 05, 2019 5:29 pm
Forum: Hydrus 1D
Topic: Competitive sorption, solute concentration initial conditions
Replies: 5
Views: 284

Re: Competitive sorption, solute concentration initial conditions

I will compensate your long post with a short one: 1. No. Solute are independent, except for the first-order degradation reactions. 2. If you simulate multiple same chemicals at the same time, you should get the same results for all of them and the same results as if you simulate only one (if you ha...
by Jirka
Mon Nov 04, 2019 5:20 pm
Forum: HYDRUS (2D/3D)
Topic: Solute transport and sub-surface irrigation
Replies: 5
Views: 343

Re: Solute transport and sub-surface irrigation

HYDRUS BCs are always in fluxes (constant or time-variable) or pressure heads (constant or time-variable), never in volumes. J.
by Jirka
Mon Nov 04, 2019 5:01 pm
Forum: Hydrus 1D
Topic: How to choose solute transport reaction parameters?
Replies: 1
Views: 182

Re: How to choose solute transport reaction parameters?

I suggest that you check examples that we are posting on the HYDRUS website. For example these: https://www.pc-progress.com/en/Default.aspx?h1d-lib-nanotubes. These examples demonstrating the use of HYDRUS-1D to simulate transport and retention of functionalized multi-walled carbon nanotubes in satu...
by Jirka
Mon Nov 04, 2019 2:55 am
Forum: Hydrus 1D
Topic: Precipitation interception / root distribution
Replies: 1
Views: 166

Re: Precipitation interception / root distribution

a) I have no opinion on how to get the "a" parameter for pines. I think it should be possible to find it in the literature. b) The values entered for root distribution are relative number. Value of 10 (location 1) compare to 1 (location 2) means that the root density is 10 times larger at location 1...
by Jirka
Thu Oct 31, 2019 3:45 pm
Forum: RETC
Topic: RETC use
Replies: 1
Views: 823

Re: RETC use

Please note that the Discussion forum is not a substitution for familiarizing yourself first with technical manuals for a particular software. For RETC, that would be: van Genuchten, M. Th., F. J. Leij, and S. R. Yates. 1991. The RETC Code for Quantifying the Hydraulic Functions of Unsaturated Soils...
by Jirka
Tue Oct 29, 2019 11:22 am
Forum: HYDRUS (2D/3D)
Topic: Root uptake Parameters
Replies: 5
Views: 300

Re: Root uptake Parameters

I do not have any other guidance beyond that provided in the above- mentioned paper and in the HYDRUS texts (manuals, help). J.
by Jirka
Mon Oct 28, 2019 7:43 pm
Forum: Hydrus 1D
Topic: Non-unique inversed model result
Replies: 2
Views: 256

Re: Non-unique inversed model result

HYDRUS uses the Marquardt-Levenberg optimization method to minimize the objective function (the sum of wighted squared deviations), which is a gradient method, i.e., it searches for a local minimum. inverse.png You need to either use multiple initial parameter estimates and then select the one with ...
by Jirka
Sun Oct 27, 2019 3:53 pm
Forum: HYDRUS (2D/3D)
Topic: Root uptake Parameters
Replies: 5
Views: 300

Re: Root uptake Parameters

You really need to first understand how the model works overall. Your questions suggest that you don’t'. The manual gives the main details. The full description is in: Šimůnek, J., and J. W. Hopmans, Modeling compensated root water and nutrient uptake, Ecological Modeling, 220(4), 505-521, doi: 10.1...
by Jirka
Sat Oct 26, 2019 12:34 am
Forum: HYDRUS (2D/3D)
Topic: Handling water balance error in wet conditions
Replies: 4
Views: 254

Re: Handling water balance error in wet conditions

If you use recommended spatial and temporal discretization and iteration criteria, you should not have any problem with water flow mass balance errors. J.
by Jirka
Thu Oct 24, 2019 2:22 pm
Forum: HYDRUS (2D/3D)
Topic: Root uptake Parameters
Replies: 5
Views: 300

Re: Root uptake Parameters

A database of suggested values for different plants for the Feddes et al. [1978] model is provided in HYDRUS based on studies by Wesseling [1991] and Taylor and Ashcroft [1972]. For methodology, you can look into the original references: Feddes, R. A., P. J. Kowalik, and H. Zaradny, Simulation of Fi...
by Jirka
Thu Oct 24, 2019 2:05 am
Forum: HYDRUS (2D/3D)
Topic: Handling water balance error in wet conditions
Replies: 4
Views: 254

Re: Handling water balance error in wet conditions

There is no special treatment of mass balances under wet and dry conditions. I would assume that this may be caused by boundary fluxes (that cause wet conditions) and which are in the denominator when calculating mass balance errors. J.